Consists of natural inlets, salt-water rivers, bays, sounds and some artificial canals. Consists of 3 segments: Gulf Intracoastal Waterway which runs east from Brownsville, Texas to Carrabelle, Florida and Tarpon Springs to Fort Meyers, FL, the Atlantic Intracoastal Waterway, Norfolk, VA to Key West, FL.
Unofficial segments of the AIWW run all the way to Boston.

Referred to as "the ditch"
Tens of thousands of snowbirds travel the ditch each year

Connects Chesapeake Bay to Albermarle Sound
Included in the National Register of Historic Places
Dug completely by hand, mostly by slaves from nearby landowners. It took 12 years to complete the 22 mile waterway which opened in 1805

Get the latest ICW charts before you go.
Waterway guide, Skipper Bob's and ICW Chart kit, Salty Southeast and Active Captain are great resources. Study them before you go and get familiar with marinas, fuel stops, pump outs and grocery locations along the way.
Electronic navigation is great to have but it's wise to have paper charts or guides as a backup.
Check your insurance if a heading south during hurricane season.
Make sure you have a good set of binoculars to identify navigational aids and watch shore life.
A working VHF and handheld are important to call bridge tenders, marinas and other vessels.
Federal law provides for the waterway to be maintained at a minimum depth of 12 feet but lack of funding has prevented that. Several areas are shoaled in.

Try to plan a route to allow for stops for fuel, food and interesting local attractions.

Kow your vertical clearance height. Even though bridges are supposed to be 65 feet, some may be a little shorter.
The Julia Tuttle Bridge in Miami ( mm 1087.2) has fixed clearance of 56' Boats taller than that must exit the waterway at Port Everglades and re enter no closer than government cut, Miami

Know the clearance of these individual bridges and what schedule they run on. For us sailors, we will have to request or wait for an opening. NC bridges channel 13 and SC bridges on channel 9
Know the protocol for passing through, waiting for the signal from the bridge tender.